While the tweet does not relate to the allegations against McAlpine, libel cases are treated in the context of their publication and can include innuendo.

Unlike in criminal law, the burden of proof is on the defendant so Bercow will have to prove she did not defame McAlpine.

"It gets into your bones, it makes you angry, and that's extremely bad for you to be angry, and it gets into your soul and you just think there is something wrong with the world," he told BBC Radio 4's World at One in an emotional interview.

"They could have saved themselves a lot of agonising, and money actually, if they had just made [a] telephone call.

"They should have called me and I would have told them exactly what they learned later on - that it was complete rubbish and that I had only ever been to Wrexham once in my life."

McAlpine's unwanted battle with the BBC has so far cost the corporation its director-general and seen several senior news managers suspended pending an internal inquiry. It also brought scandal back to the BBC's front door, as it struggled to respond to wide-ranging criticism from the press.

His solicitor, Andrew Reid, told BBC Radio 4: "Lord McAlpine is more than aware that the ultimate people who will paying for any monies that he may receive are in fact the licence payers, the people who really own the BBC, and he is very much aware of this and hence any agreement that is reached is tempered in the light of that."

The BBC currently has several inquiries into the McAlpine affair and its mistakes over Jimmy Savile.

Yesterday, peers suggested the probe into the original inquiry into the abuse of children in north Wales should be cancelled, but Downing Street is pressing ahead with it.